Crimping method and apparatus



Nov. 29, 1966 R. J. Lor-'TIN ET AL 3,287,784

CRIMPING METHOD AND APPARATUS RICHARD S. ROBERTS Nov. 29, 1966 R. J. Loi-'TIN ET AL 3,287,784

CMMPING METHOD AND APPARATUS 5 Sheets-Sheet 2 Filed Deo. 29, 1965 INVENTORS wml ROBERT J. LOFTIN RICHARD S. ROBERTS Nov. 29, 1966 R. .LLOFTIN ET AL CRIMPING METHOD AND APPARATUS 5 Sheets-Sheet 3 Filed Dec. 29, 1965 F /GUE 4 FIGURE 5 INVENTORS ROBERT J. LOFTIN RICHARD S. ROBERTS NOV. 29, 1966 R. J. LOFTIN ET AL 3,287,784

CRIMPING METHOD AND AP'PARATUS Filed Deo. 29, 1965 5 Sheets-Sheet 4.

F /GURE 60 F/GURE 8 ,3 INVENTORS ROBERT J. LoFTlN R|CHARD s. ROBERTS Nov. 29, 1966 R. J. LOFTIN ET AL 3,287,784

CRIMPING METHOD AND APPARATUS Filed Dec. 29, 1965 5 Sheets-Sheet 5 FIGURE 9 FIGURE /0 INVENTORS ROBERT J. LOFTIN RICHARD S. ROBERTS United States Patent 3,287,784 CRIB/IPING METHOD AND APPARATUS Robert I. Loftn, Spartanburg, S.C., and Richard S. Roberts, Stamford, Conn., assignors to Celanese Corporation of America, New York, NX., a corporation of Delaware Filed Dec. 29, 1965, Ser. No. 517,347 13 Claims. (Ci. ZS-l) This application is a continuation-in-part of our applications S.N. 207,356 filed on July 3, 1962, now abandoned.

The present invention relates to a novel process and apparatus for producing a relatively high degree of crimp in a synthetic fiber material. It particularly relates to a synthetic ber product in which a relatively high degree of bulk can be developed.

As employed herein, the term fibrous material or fiber product has reference to a strandular structure in which the fibrous material or product generally comprises a plurality of continuous filaments, e.g., a filamentary tow in which substantially all of the filaments extend substantially longitudinally, i.e.,v in parallel direction. While the invention is subsequently described with reference to the treatment of a strand comprising continuous filaments, the crimping, setting, and other operations, hereinafter described, may be carried out with the strand comprising discontinuous material, such as staple fiber slivers, rovings and the like, with minor modifications as called for. Moreover, various steps can be effected continuously or batchwise1 depending upon the sizes of the runs and other conditions. Two or more strands can be processed simultaneously either above, alongside, or spaced from one another. When different strands are superposed and then stapilized as on a Continuous process tow-to-top machine such as the Turbostapler, or drafted if already stapilized, a blend yarn can be produced. When spaced laterally, a single apparatus can be used to process several tows simultaneously. Although the strand is subsequently described with particular reference to cellulose triacetate, it may comprise one or more strands of any filamentary material having thermoplastic properties, which may include, e.g., secondary cellulose acetate, nylon, polyesters nitriles, acrylics, polymers and co-polymers of other vinylidene monomers.

It is known to deform fibrous materials such as tows, slivers, roi/ings, and the like whereby crimps, i.e., deviations from the linearity of the fiber are formed therein to provide for greater fiber-to-fiber cohesiveness and/ or to subsequently provide a low density, bulky or voluminous yarn per se or to provide bulk in a finished fabric. Cohesiveness among fibers is highly desirable in order to make easier subsequent processing, eg., staple processing, and to provide greater yarn integrity. Bulky, voluminous yarn or yarn which has a built-in tendency to bulk is also highly desirable because it provides finished fabrics of much more pleasing hand and aesthetic properties. Moreover, voluminous yarns are desirable because they prov-ide fabrics of greatly improved cover, i.e., better yield from less yarn and of enhanced insulating properties.

Fiber-to-fiber cohesiveness and bulking properties are known to depend upon the lack of fiber linearity; i.e., the greater the number of crimps, the more enhanced is the cohesiveness and the bulk. Moreover, the character of the crimp, i.e., the amount of crimps per inch, crimp amplitudes, etc., is also of significance in the enhancement of the above mentioned desirable properties. Crimp creates air spaces between continuous filaments; the amount of and number of air spaces determines ultimate bulk in a lamentary product or covering power in a fabric produced from such product.

farice It is also known to deform, i.e., to crimp fibrous materials, such as above mentioned, in a variety of ways such as gear crimping, stufiing box crimping, false twisting, jet bulking with air or steam, knit-de-knit, and the like. While these processes and the corresponding apparatuses produce satisfactory results in some instances, and for some end uses, it is sometimes found that the fibrous material may be unduly damaged physically or the bulk is not permanent or is not sufficiently high or the like. In addition, the apparatuses are sometimes expensive to fabricate and operate, and are delicate or incapable of wide latitude in operation. Moreover, it has not been possible heretofore to provide crimp in brous material, which crimp is of the high degree of uniformity, i.e.y without skips Skips are defined herein as positions along the length of the fibrous material which are not crimped, or at least are not crimped to the same degree as are adjacent lengths of the fibrous material. Skips in a fiat, ribbon-like filamentary tow or bundle of continuous filaments results in crimp variation longitudinally and laterally of the ribbon, e.g., the ribbon edges may not be crimped at all, or one unit length of ribbon is crimped to a higher or lesser degree than are adjacent ribbon lengths. Such nonuniformity results in nonuniformity of cover in the case of finished fabrics, as well as problems in dyeing and finishing of the fabric. In addition, where such nonuniformly crimped fibrous products are used in cigarette filters, uneven pressure drop and therefore channelling occurs in filtering the tobacco smoke. Further, it has not been possible heretofore to produce fibrous products having relatively high degree of crimp, i.e., above 12-15 crimps per inch without substantial damage to the physical properties of the fibrous material.

In conventional stuffer box crimping of brous material, the fibrous material is forced into a rectangular shaped confined chamber or zone defined by four plates, as is shown, e.g. in United States Patents 3,022,545 and 3,120,692, which patents are deemed exemplary of the stuffer-box crimping ar-t. The fibrous material is retarded in its forward movement by an accumulated mass of the fibrous material within the Zone, such mass forming a back pressure against the forward movement of the incoming fibrous material. The fibrous material is caused to accumulate because of a gate-like member closing ofic the exit of the crimping zone. Incoming fibrous material rapidly decreases in its forward speed through the zone because of this back pressure and as a result begins deforming lengthwise in a generally saw-too-th pattern. Contrary to gear crimping or knit-de-knit crimping, which produces crimp which is of generally uniform size and which is rounded at the apices or nodes thereof, crimp produced according to convention-al stuffing box methods is generally irregular and sharp pointed. Crimp amplitude and its frequency depends upon the zone depth and the crimping force upon the fibrous material. Crimping force being a function of the difference between the force retarding forward movement of the fibrous material through the zone and the force impelling the fibrous material within the zone. When the force of the incoming brous material exceeds that of the gatelike member and the frictional forces between the fibrous material and the crimping zone walls lor plates, then the crimped fibrous material continues in its forward movement. One can readily see that such operation by its very nature must be somewhat intermittent and results in a fibrous product having skips and damaged edges. Instead of a dynamic situation continuously existing, in the usual stuffer box crimper, there is a combination of a static-dynamic operation. This results in poor utilization of the available crimping energy. Instead of all or substantially all of the available crimping force being utilized to crimp the fibrous material, some of it is dissipated in overcoming inertia of the fibrous mass as well as the inertia of the gate-like restricting member.

It is accordingly the primary object of our invention to provide a relatively highly crimped fibrous product.

It is another object of our invention to provide a synthetic fibrous product having high bulking properties.

A further object is to provide a method and apparatus capable of imparting a relatively high level of crimp of various frequencies and amplitudes .to a fibrous material.

Still another object of the invention is to impart to a fibrous material a highly uniform crimp without reducing the physical properties unduly.

Still a further object of the invention is to provide a method for producing a highly bulked fibrous product.

Another object is to provide an improved stuifer box like crimper capable of imparting a higher crimp level to fibrous material without unduly reducing the physical properties.

An additional object of our invention is to provide a process and apparatus for crimping fibrous material which are not attendant with the above-mentioned disadvantages.

Other objects and advantages of the invention will become apparent from the following detailed description and claims. v

In accordance with one aspect of the invention, a filamentary strand such as a tow, i.e., a bundle of substantially parallel continuous filaments, is continuously forced lengthwise into a stuffer box like low chamber or zone formed by two substantially parallel plates, hereinafter further described, by means of a rotating roller forming a nip with a corner of one of the plates. Our stung box-like chamber, contrary to usual stufling box crimping zones has no side plates to laterally confine the tow. A second roller operating at a slower speed retards forward movement of the tow thereby causing it to bunch up lengthwise inside the chamber and thereby to take on a relatively high degree of crimp which is quite unexpectedly, the crimp produced according to our process permanent and has a sinewave-like appearance, unlike the saw-tooth appearance of crimp produced on conventional stuffer box crimpers. In contrast with conventional stuifer box crimping, cellulose triacetate and secondary acetate crimped according to our invention is of relatively high frequency and low amplitude. The amplitude and frequency of the crimp are dependent upon how high the chamber is and the relative speeds of the rolls. The height of the chamber in a section transverse to the general direction of advance of tow therethrough is desirably less than about 3,'/8 inch, advantageously less than about l/r inch and preferably less than about 1%; inch. Excellent results and high levels of crimp with minimum damage to the fiber have been achieved at heights of 1/16 or 1/32 inch. The minimum vspacing possible for practical reasons is about 1,64 inch. The height to achieve a selected degree of crimping will be dependent to some extent on the cross-sectional make-up of the tow, i.e., a heavy compact tow will require a greater height whereas if the same tow is spread out laterally a lesser height would be suitable. The maximum height of the chamber is desirably 9%; inch, as above-mentioned. The chamber should not be so high that appreciable folding over of the fibrous material lengthwise on itself occurs, or shaking, i.e. lateral spreading of the fibrous material occurs, in order to fill the chamber. Such excessive height results in dissipation of crimping force, i.e., the compressive force required to collapse the fibrous material, and undue damage thereto. Moreover, it results in crimp of a less permanent nature, which may be readily pulled out in subsequent processing. It is noteworthy that in the practice of our invention the spacing of the plates is so close and there is so much force on the fibers that they do not shift laterally to any great extent, e.g., if the tow fed into the 'chamber is 1/2 inch wide, the chamber should be at least about 1 inch wide to 'tow inside the chamber.

permit some lateral expansion, but it is not of consequence if the chamber were 3 inches wide instead. The width of the chamber should, however, be substantially wider than the width of the tow ribbon being crimped. This will allow for any lateral expansion of the ribbon caused by the pressure of the roller thereon and prevent any undue damage to the fibers at thel edges of the ribbon. Of greatest importance, however, it is discovered that such lack of lateral confinement results in a very uniform crimp laterally across the ribbon, i.e., the crimp at the edges of the ribbon has substantially the same character as that at the middle thereof. The length of the chamber desirably is at least about 1/s inch; usually it is no more than about fm inch long; and if the chamber is longer than necessary to impart the desired amount of crimp, i.e., about one inch, excessive damage may be done to the fibrous material, apparently because of the abrasive action of the chamber walls upon the fibrous material.

The length of the chamber to some extent is dependent upon the differences in roll speed, i.e., the tow desirably is subjected to the crimping force within the chamber for at least a fraction of a second. It is this crimping force which determines the permanence of crimp in the fibrous material, i.e., the higher the crimping force, the greater is the crimps per inch, and the less likely are the crimps to be pulled out in later processing, Apparently, but we do not wish to be limited by this theory, a crimp becomes permanent because .at that point the fiber has become permanently deformed due to the fact the compressive strength of the fiber has been exceeded. No advantage is gained, in fact damage may ensue by increasing the length of the ychamber beyond one inch and consequently the dwell time of the tow therein. The concept of dwell time and chamber length can be expressed somewhat differently, viz., in terms of the length of the T he length of tow in the chamber, on an uncrimped basis, is usually at least about twice the length of the crimped tow, measured after withdrawal from the chamber. Preferably, the length of tow on an uncrimperl basis is no more than about seven times the length of the crimped tow. However, under certain conditions wherein fiber strength may be a lesser consideration, the length of tow on an uncrimped basis may be more than seven times the length of the crimped tow. It may, eg., be as much as ten times the length of the crimped tow.

The crimped tow may then be subjected to a crimp setting treatment as by hot air, radiation, steam or hot water, in which case subsequent drying will be required. Such treatment may either be of a batch or continuous nature. It may then be put t0 whatever uses other crimped tows have been put, eg., making staple fibers for yarns and especially for tiberfills, nonwovens, cigarette filters, and the like. The extremely high crimp of the product gives special advantage in these end uses. Whether or not setting of the crimp is undertaken, the crimp because of our more positive control on backpressure is exceptionally uniform with no skipped spots as oftentimes occurs with conventional stuffing box crimpers. Moreover, a higher degree of crimp with less fiber damage is produced than in known stulfer box crimpers. 'In the conventional stuifer box crimper one may obtain, e.g., an average of about l2'crimps per inch while in the practice of our invention one can obtain from at least 4about 15 crimps per inch to in excess of 50 crimps per inch. While conventional gear crimping will also produce a regular uniform crimp, it is not widely used because it frequently results in excessive damage to the fibers, in contrast with the present invention wherein the physical properties of the iilamentary material after crimping are almost equal to the properties before crimping.

For example, calculated on the basis of an inch of tensioned ber, that is a `liber that has had the crimp pulled out to such extent that it is essentially straight and then relaxed and the crimps counted which remain in a measured inch, the novel apparatus permits easy insertion of more than about 15 crimps per inch, and even in excess of 50 crimps per inch. Frequently, even with tows of substantial bulk more than 25 regular crimps per inch are achieved, and after crimping the tensile factor, viz., -tenacityxthe square root of elongation or TEV2, is more than 2/3 and frequently more than 3A of its value before crimping. Such crimping has not heretofo-re been possible.

In accord-ance with another aspect of the present invention, the ilamentary strand subjected to such high level crimping comprises cellulose triacetate, and preferably cellulose triacetate exhibiting a tensile factor of at least about 9 and preferably at least about 10 such -as may be produced by wet spinning as described in U.S. Patent 3,057,039, in the name of Jesse L. Riley, or in U.S. Patent 3,071,806, in the name of Arnold J. Rosenthal. The crimp in the triacetate filaments having a crimp level of at least 15 crimps per inch is set by steaming, preferably with saturated steam at about 212 to 300 F., and even more preferably about 240 to 270 F. While even a fraction of a second is suicient to heat set a single fiber, the duration of heat setting should be long enough to ensure that all of the 'fibers in the strand reach the desired temperature. The heat setting achieves crystallization f the lfilament-forming molecules and so renders them more resistant to subsequent thermal treatments, e.g., raises the safe-ironing temperature and dimensional stability of fabrics thereof. Moreover, heat setting cre- -ates a crimp memory into a fiber. Often during subsequent processing the crimp is pulled out of the ber, or at least the angle of crimp is increased, i.e., there are less crimps per inch, and the amplitude thereof is lessened. However, the original crimp may be restored by a hot relaxing treatment.

The high level of crimping may be produced most preferably by the aforementioned apparatus of our invention; however, it may also be produced by apparatus such as is described in U.S. Patents 2,765,513 and 2,765,514, the disclosures of which are herein incorporated by reference. Conveniently, it can be effected continuously with the production of the tow, the washing of the tow serving as a pretreatment to crimping. The wet tow is then crimped to the indicated level and the crimp is set, the crimped filaments in the tow usually retaining in excess of about 1/2 of their tensile factor in the absence of such crimping which latter will usually exceed 9 and frequently exceed 10; the tensile factor of the crimped tow may be as much as 8, sometimes as -much as 10 and frequently even higher, depending on the value for the initial tow.

The filamentary strand at this point is characterized by exceptionally high bulk. It is also exceptionally suited for use in cigarette filters both as a result of the bulk and high crimp, either in set or unset form. If used for making staple fiber yarns, however, the drafting, twisting and/or breaking operations will most often tend to pull out the crimp as above-mentioned; however, because of the previous crimp setting, such loss is only temporary and after processing the yarn and/or a fabric made therefrom can be re-bulked by a hot relaxed treatment, employing `dry heat tumbling, steam, or hot water either before, after or during dyeing or any other treatment. Yarn so treated resembles high bulk wool yarns, which has not heretofore been possible with cellulose triacetate, and may be used in place thereof in hand or machine knitting. The specific volume of such yam may exceed 10 and frequently exceeds 12 cc. per gram.

The invention will now be described in detail with reference to the accompanying drawings wherein:

FIG. 1 is a schematic perspective view of an apparatus for converting a tow into a bulked staple fiber yarn;

FIG. 2 is an elevation, with a portion shown in section, of the pretreating and crimping elements of FIG. 1;

FIG. 3 is a top plan view of the apparatus of FIG. 2;

FIG. 4 is a perspective view of the crimping rolls, plates and `drives of FIG. 3 with portions broken away and/or omitted for ease of understanding; the observer is located at the legend FIG 3 relative to the apparatus of FIG. 3;

FIG. 5 is an enlarge-ment of a portion of the apparatus of FIG. 2, with the side wall near the observer removed;

FIGS. 6, 7 and S are enlargements of FIG. 5 with the ple-.tes shown in different operative positions to effect different crimping;

FIG. 6a is a lateral elevation of a portion of an alternative apparatus showing the slope of the working surface of plate 16;

FIG. 9 is a lateral elevation of a portion of a different embodiment of a crimping apparatus according to our invention;

FIG. 10 is a lateral elevation of a portion of an alternative crimping apparatus;

FIG. 11 is a schematic perspective view of an apparatus for converting a tow into cigarette filters; and

FIG. l2 is a perspective view of a filter cigarette with a portion of each paper wrapper broken away.

Referring now more particularly to the drawing, in FIG. 1, there is shown a synthetic filament tow production apparatus 10 such as a wet spinning column and spinbath zone (not shown) from which there issues `a tow 11. The tow is pulled through a pretreating chamber or box 12 such as eg., a steam box having a temperature of from about to 150 degrees centigrade and lmore preferably degrees centigrade by rotating roll 13 cooperating with a fixed plate 14 to form a nip with a corner thereof whereby the tow is forced or impelled lengthwise into the crimping chamber or zone. A more slowly rotating roll 15 cooperating With a corner of fixed plate 15 forms a second nip whereby the forward movement of the tow through the crimping zone is retarded. As described more fully hereinafter, the tow is crimped through the cooperation of both rolls 13 and 15 and the opposed surfaces of both plates 14'. and 16. The tow then passes into steam box 17 wherein the crimp is set. It passes next to an opening device such as roll pairs 18, 19 and 20, 21 of which the lowers are smooth and the uppers helically grooved, to effect opening of the tow as described in detail in United States Patent 3,156,016, which patent was issued to Donald T. Dunlap and Richard E. St. Pierre. Y The now opened tow is severed into staple fibers 23 as by a cutter 22 and by means of conventional carding and twisting apparatus, shown schematically `at 24, the bers are formed into a yarn 2S which by means of rolls 26, 27, 28 and 29 is caused to pass through boiling water 30 in a tank 31 which effects bulking of the yarn upon drying (not shown). Alternatively, as hereinafter described, the opened tow leaving rolls 20, 21 may be formed into cigarette lters in known manner.

The construction and arrangement of the crimping apparatus embodying 13, 15 and plates 14, 16 are shown in detail in FIGS. 2 to S. As seen in FIG. 3 pretreating chamber 12 has a lid 32 and elongated slots 33 and 34 in its respective end Iwalls to permit entry and egress of the tow 11. An idler roll 35 extends transversely across the chamber 12 parallel to slots 33 and 34 and serves both to lengthen the path of the tow in the chamber and to ensure contact between the tow and the pretreatment medium near the bottom of chamber 12. This medium may be gaseous as in the case of steam or it could be a liquid pretreating agent such as water, either hot or cold in which case the roll 35 would cause the tow to be submerged in the liquid; the treating agent is admitted to chamber 12 through pipe 36.

Tlhe tow 11 is then pulled alo-ng by roll 13 through the space between roll 13 and the corner of plate 14 `and is forced or impelled int-o the narow passageway 37 (FIG. 6) whose upper and lower walls are constituted by substantially parallel opposed working faces of plates 14 and 16. Roll 15 is rotating in a counterclockwise direction, as shown by the arrow, at a lesser peripheral speed than roll 13 in order to uniformly positively control the exit of the tow from passageway 37, the tow passing between roll land the corner of plate 16 as shown in the drawing. The peripheral speed of roll 15 is less than that of roll 13 so that forward movement of the tow through the passageway 37 is retarded. The gradual decrease in speed of the tow through the passageway results in an accumulation of tow thereby creating -a backpressure on incoming tow. As one can readily see, this backpressure is determined both by the speed of r-oll 15 and the friction Ibetween the tow and the walls of passageway 37. Consequently, the feeding of additional tow into the passageway by roll 13 can only be effected with force and this results in crimping of the tow is said passageway. Quite unexpectedly there is substantially no lateral movement of the tow although there are no confining side walls .and it is tightly compacted in the passageway and is retarded in its forward movement. Evidently, and we do not wish to be limited by this theory, the force on the tightly compacted tow in combinaion with the relatively narrow spacing between plates 14, 16 substantially preclude lateral movement. The spacing between the plates determines the crimp amplitude and the relative roll speeds determine the degree of crimping, i.e., the number 4of crimps per inch. The spacing should not be such as to allow any substantial overlapping lengthwise of the tow ribbon on itself.

It will be noted that the working, i.e., opposed, faces of plates 14 and 16 are inclined relative to the thickness of the plates. The .angle of inclination of the working face with respect to the thickness of the plate depends largely on the distance between the roll surfaces, i.e., the length of the crimping chamber. The angle may vary from about 10 to about 60 degrees. However, in order to better doctor yarn from roll 13 into'pass-ageway 37 a relatively blunt angle is found to be highly desirable, e.g. about 3G degrees. If the distances between the roll surfaces is close, as for example is shown in FIGURE 9, then the angle can readily be made blunt. If however, the distance between the roll surfaces is greater, as for example is shown in FIGURE 6, then at least the initi-al angle should be made blunt, as is shown in FIGURE 6a. T o more fully explain, attention is invited to FIGURE 6a, wherein the initial angle 0, is shown to be greater than the slove angle 62 of the working face of plate 16 with respect to the thickness of the plate. Quite unexpectedly, it is found that less fiber damage occurs and there is better feed in to passageway 37 with a blunt initial angle. As is shown in FIGURE 6a, the corner of plate 16 should be almost inv contact with roll 13 and tangent thereto in order to preclude damage to 4the fibrous material being crimped and to prevent its wrapping around roll 13. This inclination facilitates entry of the tow into passageway 3-7 and aids movement of the tow therefrom as contrasted with the use of plates so disposed that the longitudinal axis of the passageway defined therebetween were perpendicular to the line joining the roll centers, or at a greater lesser angle than stated above.

As shown in FIGS. 4 and 5, the rolls 13 and 15 are preferably rubber covered; however, they could be rigid and spring mounted to be yielding. They could also be of roughened steel or the like material which would provide positive control over the fibrous material. As is quite obvious, to provide proper utilization of the crimping force there should be no slippage between the fibrous material a-nd rolls 13, 15. They are driven at independently controllable sepeeds by variable speed drives 38, 39 through the intermediaries of sprocket Wheels 40, 41 and 42, 43 plus sprocket chains 44, 4S. The rolls 13 and 15 are mounted between a pair of side walls 46, 47 respectively provided with slits 48, 49, each of which includes a generally horizontal portion and an inclined portion. As

can be seen in FIGS. 2 and 4, the horizontal portions of the slits serve to guide the sides of plate 14 whose position relative lto roll 13 can Ibe adjusted by means of threaded bolts 50. The sides of plates 16 are threadedly connected by lbolts 51 to pos-itions S2, 53 which extend.

, to a retracted position (not shown) wherein its working face defining passageway 37 is spaced a considerable distance from the working-face of plate 14, in which position the apparatus can more easily `be threaded up. Bolts 51 allow for a fine adjustment `of the size of passageway 37.

As shown in FIG. 3, a grooved wheel 59 may be mounted for rotation with sprocket wheel 43. A belt 60 trained about a second grooved wheel 61 causes the latter to rotate with roll 15. A roll 62, mounted between brackets 63, 64 carried by side walls 46, 47, is connected to grooved wheel 61 so as to be rotated thereby. Preferably the coupling between roll 15 and roll 62 is such that the later rotates more slowly than the former while guiding the crimped tow either to the next operationor into a tow can for storage prior to the next operation; the rotation of roll 62 also serves to prevent pile up of the tow in the space between side walls 46, 47. Advantageously a fiat sheet 65 is connected to the real, i.e., nonworking end, of plate 16 and extends toward roll 62 so as to provide a support for two moving between rolls 15 and 62 thereby protecting the tow from entanglement with or contamination by the equipment.

The manner in which the amplitude and degree of crimping can be controlled by the apparatus so far described can best be understood by a comparison of FIGS. 6, 7 and 8. In each of these figures the roll 13 is operating at the same speed, the position of plate 16 relative to rolls 13 and 15 is the same and in each the roll 15 is operating at a lesser peripheral speed than the roll 13. However, in FIG. 7 roll 15 is operating faster than in FIG. 6, and as a result the crimp frequency is lower in FIG. 7. In FIG. 8 the speed of roll 15 is the same as in FIG. 6 but passageway 37 is narrower, i.e., plate 14 has been displaced to the right. Consequently, the amplitude is different than in FIG. 6, i.e., the amplitude is lower. The frequency, however, is not the same even though the relative roll speeds are the same in both instances. Crimp frequency is determined as hereinbefore mentioned on the basis of an inch of tensioned fiber,

. which is subsequently relaxed, and the crimps counted.

It has been'determined that amplitude and frequency are not totally dependent on one another; the greater is the crimping zone depth, i.e., the greater the amplitude of crimp, the lower is the frequency of crimp likely to be. Conversely, we have discovered that the lower the amplitude, the higher is the frequency of crimp.

As stated hereinbefore, it is the crimping force which determined the permanence of crimp. However, this also determines the frequency of crimp, although to a certain extent such is influenced by the depth of the crimping chamber. Crimp formed within the crimping chamber due to excessive chamber depth is not, however, of the same degree of permanence as that formed solely by the crimping force without overlapping of the material being crimped. The crimping force is determined by the difier- 'ence between the peripheral roll speeds. The greater the difference, the greater is the crimping force. Suitable crimping force is obtained when the peripheral roll speeds are in a ratio of from about at least 2 to 1 to about 10 to 1. Preferably, however, the roll speeds are in a ratio of from about 4 to 1 to about 6 to 1. Expressed in another way suitable crimping is obtained according to our invention when the force created by the feed roll 13 and the retarding force created by roll 15 is in a ratio of from about 2 to 1 to about l0 to 1, and more preferably from about 4 to l to about 6 to l. Below a crimping force of about 2:1, we have found that the crimp is not permanent, and for some unexplained reason the amplitude is large regardless of crimping chamber depth. Apparently, but we do not wish to be limited by this explanation, the fibrous material in forming crimp shrinks to such an extent that the crimping zone is not filled suiciently to create enough backpressure to obtain a satisfactory crimping force. Above a crimping force of about 10 to 1, considerable damage is done to the fibrous material.

In FIG. 9, there is shown a different embodiment of an apparatus which may be employed to crimp a fibrous material in accordance with the present invention. Specilically, the length of passageway 37, greatly enlarged in the drawing, is considerably shorter than in the embodiment of FIGS. to 8. It may be, for example, Vs inch long. This requires a closer positioning of rolls 13 and 15, which may be, for example, 4 inches in diameter. To accommodate for this, it would be possible to reduce the thickness of the plates; instead, however, the plates have been replaced by plates 14a, 16a whose cooperating portions have been contoured to allow them to approach one another closely notwithstanding the closeness of the rolls. It is understood by those skilled in the art, however, that roll size is not critical and may ybe of any desired size. The contoured or curved outlet makes more positive the backpressure in the crimping zone.

In FIG. there is shown a different apparatus which can also be employed for crimping. This apparatus is described more fully in U.S. Patents Nos. 2,765,513 and 2,764,514, particularly with reference to FIG. 5 thereof, the disclosures of said patents as before stated being incorporated herein by reference. The tow is pulled along by a relatively fast moving roll 13 between the roll and a plate or indentor 14b. It is forced into the crimping chamber or zone defined by the nip between rolls 13, 15; the tow being retarded in its forward movement through the zone by slower moving roll 15. The accumulation of tow within the zone results in crimps being formed as described above. The frequency of the crimp is controlled by the ratio of the speed of roll to the speed of roll 15. Crimp amplitude is controlled by the distance between the nip point formed by roll 13 and indentor 141; and the nip point formed by rolls (13, 15). Rolls 13, 15 both simultaneously Contact an individual crimp, one at the peak and the other at the trough; this is in contrast with the embodiments of FIGS. 5 to 9 where one plate contacts a crimp peak while the other plate simultaneously contacts the trough of the crimp, but the rolls do not simultaneously contact the peak and trough, respectively, of a single crimp. While in the above embodiments the faster moving roll has been shown as lowermost it could be made uppermost without changing the principle of operation.

Thus, all three of the above embodiments include means providing a continuous material-gripping surface movable t-hrolugh an end-less path, e.g. (roll 15), a power drive (43) associated therewith for moving said surface at a uniform rate of speed through said path, and mechanism for continuously |feeding `(e.g. roll `13 and associated power drive) a filamentary strand towards said gripping surface at a uniform speed I.greater by a predetermined inc-rement than the speed of said gripping surface to a point of advance close to said gripping surface and beyond which it undergoes an abrupt reduction in speed during its travel between said point of advance and the line of its first engagement with said gripping surface, said mechanism including means providing a continuous material-feeding surface opposed to said ygripping surface and also movable through an endless path (roll 13), said path having a section in which said materiahfeeding surface (13) converges towards said gripping surface (15) and into at least transient parallelism therewith, `a. power drive `(42) in driving relation to said last-named means for moving said material-feeding surface at a uniform rate of speed greater than that of said gripping surface,

said mechanism also including an indentor element (14) having an edge extending transversely across said feeding surface and arranged to permit said material to pass between said edge and said feeding surface, said element having a narrow -materialJpressing portion adjacent said edge, and supporting means adjustab-ly holding said element so that only said narrow portion presses the advancing material into positive non-slip frictional feeding engagement with said material-feeding surface only lalong a fixed line spaced closely in ladvance of said line of first engagement of said material with said gripping surface. In the embodiment of FIGS. 5 to 9 the zone beyond the edge is passageway 37 whereas the Zone beyond the edge in FIG. 10 is defined by the nip between rolls 13 and 15.

In FIG. 11 there is shown 'another apparatus for treating tow and converting it to another end product. Up until rolls 20, 21 the yapparatus is the same as in FIG. 1. Then the opened tow ente-rs a plasticizing chamber 66 wherein a plasticizer is applied thereto. The tow is then condensed at 67 in known manner itno a relatively small bundle `68, is wrapped in paper 69 to produce a continuous lfilter plug 70 which is then cut at 71 into filter rods y72 of predetermined length, collected at 73 to be cured, and incorporated into filter cigarettes '74 (FIG. 12) in conventional manner. Filter cigarette 73 comprises rod 72 (composed of plasticized tow and paper wrapper), tobacco 75 and paper wrapper 76 encircling them both.

The invention will be described further in the following illustrative examples wherein parts are by weight unless otherwise `speciiied.

Example I A 21.8% solution of cellulose triacetate, having an acetyl value of 61.5% and an intrinsic viscosity of 2, dissolved in 91/9 methylene chloride/methanol is wet spun into 43/ 57 methylene chloride/methanol at 32 C. through a column provided with a constriction to produce a 3 denier per filament lcow. A bundle of 20,000 such filiaments is gathered into .a tow, washed with methanol in four stages and then with water in two stages. If dried and collected at this point the laments have a tenacity of 2.6 |grams per denior, an elongation of 23% and a tensile factor o-f 12.5. Instead of being dried, however, the tow is processed generally `as illustrated in FIG. 1. The height of passageway 37 is 1/16 inch and its width is 12 inches. The roll 13 is positively driven at a peripheral speed of 261 feet per minute while roll 15 is positively driven at a peripheral speed of 87 feet per minute. Phe length of passageway 3.7 is 5% inch, the dwell time of tow therein is 0.04 second and the length of tow therein is 1.5 inches based on the length fed. The product, having 25 crimps per inch, is dried in a not air oven. The dry tow is then collected in a contained and autoclaved with saturated steam at 270 F. for 20 minutes. The crimp set tow is then opened by passage `between roll sets 18, 19 and 20, 21 of which the lower are driven and have rubber surfaces while the upper are steel and have helical threads cut into their surfaces. The product is thereafter broken on breaker rolls into 5 inch staple iibers and formed into a 16 worsted count yarn with 5 Z turns per inch; two such yarns are plied together with 3 S turns per inch to form a yarn. Upon immersion in water at 1180" F. for 30 minutes followed by tumble drying the produce has a specific volume in excess of 10 cc. per gram under a load of 1.25 pounds per square inch, eg., 12 cc. per lgrarn. In addition, the fibers exhibit the other properties characteristic of this `type of wet spun cellulose triacetate, viz., 'a high energy of rupture, radial uniformity, a pebbled surface, an overall birefringence when completly saponitied of above about 0.031 and generally of Iabout 0.0314 to 0.037, rubbery properties at 220 C. and resistance to creep at 1688" C.

l l Example Il A tow of 50,000 total denier produced as in Example I is processed as therein described through the opening step. The tow is then tplasticized with 7% of its weight of glycerol triacetate -by passage through a mist thereof, is condensed, Wrapped in cigarette paper into filter rods, cut into short lengths and incorporated Ias the tips of filter cigarettes.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention what we desire to secure by Letters Patent is:

ll. Method for crimping a fibrous material which cornprises passing said fibrous material through an apparatus comprising means providing a continuous material-gripping surface movable through an endless path, a power drive associated therewith for moving said surface at a uniform rate of speed through said path, and mechanism for continuously feeding fibrous material towards said gripping surface at a uniform speed greater by a predetermined increment than the speed of said gripping surface to a point of advance close to said gripping surface and beyond which it undergoes an abrupt reduction in speed during its travel between said point of advance and. the line of its first engagement with said gripping surface, said mechanism including means providing a continuous material-feeding surface opposed to said gripping surface and also movable through an endless path, said path having a section in which said material-feeding surface converges towards said gripping surface and into at -least transient parallelism therewith, a power drive in driving relation to said. last-named means for moving said material-feeding surface at a uniform rate of speed greater than that of said gripping surface, said mechanism also including an indentor element having an edge extending transversely across said feeding surface and arranged to permit said material to pass between said edge and said feeding surface, said element having a. narrow materialpressing portion adjacent said edge, and supporting means adjustably holding said element so that only said narrow portion presses the advancing material into positive non-slip frictional feeding engagement with said material-feeding surface only along a fixed line spaced closely in advance of said line of first engagement of said material with said gripping surface.

2.- Method according to claim 1 wherein the fibrous material is cellulose acetate.

3. Method according to claim 2 including the further step of setting the crimp in said fibrous material.

4. Method according to claim 3 including the further step of forming said fibrous material into a staple fiber yarn, and thereafter hot relaxing said yarn whereby said yarn is bulked.

5. Method of deforrning a relatively fiat, ribbon-like fibrous material comprising a plurality of individual continuous filaments in substantially -parallel alignment with respect to one another comprising the following steps:

(a) feeding said fiat, ribbon-like fibrous material lengthwise into a zone comprising a pair of substantially parallel plates under a first force;

(b) reta-rding the exit of said fibrous material from said zone by a second force less than said first force and opposed to said first force, said second force forming a substantially uniform backpressure upon the fibrous material within the zone whereby said retarding force causes said ribbon to slip lengthwise with respect to said parallel plates and to thereby form crimps of at least l5 crimps per inch, said crimps being substantially uniform lengthwise of the ribbon and extending laterally across the ribbon and being substantially normal to the lengthw-ise direction of the ribbon lof fibrous material.

6. Method according to claim S wherein the ratio of the first force to the second force is in the range of from about 2 to 1 to about 10 to l.

7. Method according to lclaim 5 wherein the plates are spaced apart at a distance of less than 3%; inch.

8. Method according to claim '7 wherein said zone has a length less than about l inch.

9. Method according to claim 8 wherein the fibrous material is cellulose acetate.

l0. Method according to claim 9 including the steps of:

(a) setting the crimps in the fibrous material;

(b) forming said fibrous material into staple fiber yarn;

and thereafter (c) hot relaxing said yarn whereby said yarn is bulked.

11. Apparatus for crimping fibrous material comprising:

(a) pair of spaced apart plates having first surfaces opposed to one another and being substantially parallel, said plate surfaces defining a confined zone having a first end and a second end and having a width substantially greater than its height; and

(b) a pair of spaced-apart right cylindrical rolls operating at first and second speeds having their axes parallel to one another and cooperating with said first and second ends of said zone to force said fibrous material into said zone and to retard its exit from said zone whereby said fibrous material is caused to form crimps therein, said rolls being arranged with respect to said zone so that an imaginary plane passing through the roll centers forms an angle of between about l0 degrees and 60 degrees with an imaginary plane parallel to the said plate surfaces and passing through the center of said zone.

l2. Apparatus according to claim 11 wherein the height of said zone is less than about 3/s inch.

13. Apparatus according to claim 11 including means to adjust the height of said zone, and means to adjust the ratio of said first and second speeds whereby the exit of the fibrous material is retarded more or less.

References Cited by the Examiner UNITED STATES PATENTS 2,500,690 3/1950 Lannan 28-72 3,139,664 7/ 1964 Carruthers 28-1 3,146,512 9/1964 Heijnis 28--1 MERVN STElN, Primary Examiner.

L. K. RIMRODT, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,287,784 November 29, 1966 Robert J. Loftin et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 14, for "the" read a column 6, line 55, after "embodying" insert rolls column 7, line 14, for "is" read in column 7, line 56, after "greater" insert or line 65, for "sepeeds" read Speed line 75, for "positions" read pistons column 8, line 26, for "real" read rear line 28, for "two" read tow column 9 line 4() for"ro11" read ro11 13 line 48, for "the" read that column 10, line 21, for "itno" read into line 44, for "denior" read denier line 55, for "contained" read container line 7S, for "l688 C" read 168 C Signed and sealed this 12th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

11. APPARATUS FOR CRIMPING FIBROUS MATERIAL COMPRISING: (A) PAIR OF SPACED APART PLATES HAVING FIRST SURFACES OPPOSED TO ONE ANOTHER AND BEING SUBSTANTIALLY PARALLEL, SAID PLATE SURFACES DEFINING A CONFINED ZONE HAVING A FIRST END AND A SECOND END AND HAVING A WIDTH SUBSTANTIALLY GREATER THAN ITS HEIGHT; AND (B) A PAIR OF SPACED-APART RIGHT CYLINDRICAL ROLLS OPERATING AT FIRST AND SECOND SPEEDS HAVING THEIR AXES PARALLEL TO ONE ANOTHER AND COOPERATING WITH SAID FIRST AND SECOND ENDS OF SAID ZONE TO FORCE SAID FIBROUS MATERIAL INTO SAID ZONE AND TO RETARD ITS EXIT FROM SAID ZONE WHEREBY SAID FIBROUS MATERIAL IS CAUSED TO FORM CRIMPS THEREIN, SAID ROLLS BEING ARRANGED WITH RESPECT TO SAID ZONE SO THAT AN IMAGINARY PLANE PASSING THROUGH THE ROLL CENTERS FORMS AN ANGLE OF BETWEEN ABOUT 10 DEGREES AND 60 DEGREES WITH AN IMAGINARY PLANE PARALLEL TO THE SAID PLATE SURFACES AND PASSING THROUGH THE CENTER OF SAID ZONE. 